1. Field of the Invention
The present invention relates to a liquid discharging head and a liquid discharging apparatus for discharging liquid by bubble generation for example by thermal energy, and more particularly to a liquid discharging head and a liquid discharging apparatus utilizing a movable separation membrane which is moved by the bubble.
The present invention is applicable to a printer for recording on various recording media such as paper, yarn, fiber, fabrics, leather, metal, plastics, glass, timber, ceramics etc., a copying machine, a facsimile apparatus having a communication system, a work processor having a printer unit, and an industrial recording apparatus combined in composite manner with various processing apparatus. In the present invention, the "recording" means not only forming a meaningful image such as a character or graphics on the recording medium but also forming a meaningless image such as a pattern.
2. Related Background Art
There is already known an ink jet recording method, so-called bubble jet recording method, for providing liquid such as ink with an energy such as heat to generate a state change involving a steep volume change (generation of a bubble), causing the liquid to be discharged through a discharge opening by the force based on such state change and depositing the liquid onto the recording medium to form an image. The recording head utilizing such bubble jet recording method is generally provided, as disclosed in the Japanese Patent Publication Nos. 61-59911 and 61-59914 (corresponding to the U.S. Pat. No. 4,723,129), with a discharge opening for discharging liquid, a liquid path communicating with the discharge opening, and a heat generating member (electrothermal converting member) positioned corresponding to the liquid path and serving as energy generating means for generating energy for discharging the liquid.
Such recording method is advantageous in various manners such as being capable of printing an image of high quality at a high speed and a low noise level, printing an image of a high resolution with a compact apparatus since the discharge openings can be arranged with a high density, and obtaining a color image in a simple manner. For this reason, the bubble jet recording method is recently utilized in various office equipment such as printer, copying machine, facsimile etc. and even in certain industrial applications such as fabric printing apparatus.
On the other hand, in the conventional bubble jet recording method, as the heat generating member repeats heating in direct or indirect contact with liquid, there may be formed, on the surface of the heat generating member, a deposit resulting from scorching of the liquid. Also, in case the liquid to be discharged is easily deteriorated by heat or cannot show sufficient bubble generation, satisfactory liquid discharge may not be achieved by the bubble formation by the aforementioned heat generating member.
On the other hand, the Japanese Patent Application Laid-Open No. 55-81172 proposed a method of separating a bubble generating liquid and a discharge liquid by a flexible membrane and generating a bubble in the bubble generating liquid by thermal energy thereby discharging the discharge liquid. In the configuration of the proposed method, the flexible membrane and the bubble generating liquid are so positioned that the flexible membrane is provided in a part of the nozzle, but the Japanese Patent Application Laid-Open No. 59-26270 discloses a configuration employing a large membrane separating the entire head into an upper part and a lower part. Such large membrane, being supported between two plate members constituting the liquid path, is so provided that the liquids in the two liquid paths are not mutually mixed. Also there are known configurations giving certain feature to the bubble generating liquid itself in consideration of the bubble generating characteristics, such as the one disclosed in the Japanese Patent Application Laid-Open No. 5-229122, employing liquid of a lower boiling point than that of the discharge liquid or the one disclosed in the Japanese Patent Application Laid-Open No. 4-329148, employing electrically conductive liquid as the bubble generating liquid.